S. W. Allen
A5012808007- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Gamma-ray bursts and supernovae
- Particle Detector Development and Performance
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Magnetic confinement fusion research
- CCD and CMOS Imaging Sensors
- Radio Astronomy Observations and Technology
- History and Developments in Astronomy
- Pulsars and Gravitational Waves Research
- Fusion materials and technologies
- Adaptive optics and wavefront sensing
- Medical Imaging Techniques and Applications
- Solar and Space Plasma Dynamics
- Calibration and Measurement Techniques
- Cinema and Media Studies
- Geophysics and Gravity Measurements
- Radiation Detection and Scintillator Technologies
- Advanced X-ray and CT Imaging
Stanford University
2016-2025
Kavli Institute for Particle Astrophysics and Cosmology
2016-2025
SLAC National Accelerator Laboratory
2016-2025
New England School of Acupuncture
2025
MCPHS University
2025
Michigan United
2024
University of Michigan–Ann Arbor
2024
Lawrence Livermore National Laboratory
1990-2024
Children's Hospital of Pittsburgh
2019-2024
University of Pittsburgh
2018-2024
We present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg$^2$ $griz$ imaging data the first year Dark Energy Survey (DES Y1). combine three two-point functions: (i) cosmic shear correlation function 26 million source galaxies in four redshift bins, (ii) angular autocorrelation 650,000 luminous red five (iii) galaxy-shear cross-correlation positions shears. To demonstrate robustness these results, we use independent pairs...
Studies of galaxy clusters have proved crucial in helping to establish the standard model cosmology, with a universe dominated by dark matter and energy. A theoretical basis that describes as massive, multi-component, quasi-equilibrium systems is growing its capability interpret multi-wavelength observations expanding scope sensitivity. We review current cosmological results, including contributions fundamental physics, obtained from clusters. These results are consistent complementary those...
We present constraints on the mean dark energy density, Omega_X and equation of state parameter, w_X, based Chandra measurements X-ray gas mass fraction in 26 luminous, dynamically relaxed galaxy clusters spanning redshift range 0.07-1, same data require w_X
We present a 90 per cent flux-complete sample of the 201 X-ray-brightest clusters galaxies in northern hemisphere (δ ≥ 0°), at high Galactic latitudes (ǀbǀ 20°), with measured redshifts z ≤ 0.3 and fluxes higher than 4.4 × 10−12 erg cm−2 s−1 0.1–2.4 keV band. The sample, called ROSAT Brightest Cluster Sample (BCS), is selected from All-Sky Survey data largest X-ray-selected cluster compiled to date. In addition Abell clusters, which form bulk BCS also contains Zwicky other their X-ray...
We present constraints on the mean matter density, Ω m , dark energy DE and equation of state parameter, w, using Chandra measurements X-ray gas mass fraction (f ) in 42 hot (kT > 5keV), luminous, dynamically relaxed galaxy clusters spanning redshift range 0.05 < z 1.1.Using only f data for six lowest at 0.15, which has a negligible effect measurements, we measure = 0.28 ± 0.06 (68 per cent confidence limits, standard priors Hubble Constant, H 0 baryon b h 2 ).Analyzing all clusters,...
We present a catalog of galaxy clusters selected via their Sunyaev-Zel'dovich (SZ) effect signature from 2500 deg$^2$ South Pole Telescope (SPT) data. This work represents the complete sample detected at high significance in 2500-square-degree SPT-SZ survey, which was completed 2011. A total 677 (409) cluster candidates are identified above signal-to-noise threshold $\xi$ =4.5 (5.0). Ground- and space-based optical near-infrared (NIR) imaging confirms overdensities similarly colored galaxies...
We present the first results from a very deep Chandra X-ray observation of core Perseus cluster galaxies. A pressure map reveals clear thick band high around inner radio bubbles. The gas in must be expanding outward and sharp front to it is identified as shock front, yet we see no temperature jump across it; indeed there more soft emission behind than it. conclude that this region either thermal conduction operates efficiently or co-existing relativistic plasma seen mini-halo mediating...
We report subarcsec-resolution X-ray imaging of the core Perseus cluster around galaxy NGC 1275 with Chandra Observatory. The ROSAT-discovered holes associated radio lobes have bright rims which are cooler than surrounding gas and not due to shocks. themselves may contain some hotter gas. map strong photoelectric absorption across Northern lobe rim a small infalling irregular galaxy, known as high velocity system. Two outer holes, one was previously known, identified recently found spurs...
We present preliminary results from a deep observation lasting almost 200 ks of the centre Perseus cluster galaxies around NGC 1275. The X-ray surface brightness intracluster gas beyond inner 20 kpc, which contains radio bubbles, is very smooth apart some low-amplitude quasi-periodic ripples. A clear density jump at radius 24 kpc to north-east, about 10 out bubble rim, appears be due weak shock driven by northern bubble. similar front may exist both bubbles but masked elsewhere rim emission...
Using Chandra X-ray observations of 9 nearby, luminous ellipticals with good optical velocity dispersion measurements, we show that a tight correlation exists between the Bondi accretion rates calculated from data and estimated black hole masses, power emerging these systems in relativistic jets. The jet powers, inferred energies timescales required to inflate cavities observed surrounding emitting gas, can be related by law model. A significant fraction (2.2^{+1.0}_{-0.7} per cent, for...
We present the science case, reference design, and project plan for Stage-4 ground-based cosmic microwave background experiment CMB-S4.
This book lays out the scientific goals to be addressed by next-generation ground-based cosmic microwave background experiment, CMB-S4, envisioned consist of dedicated telescopes at South Pole, high Chilean Atacama plateau and possibly a northern hemisphere site, all equipped with new superconducting cameras. CMB-S4 will dramatically advance cosmological studies crossing critical thresholds in search for B-mode polarization signature primordial gravitational waves, determination number...
eROSITA is the primary instrument on Russian SRG mission. In first four years of scientific operation after its launch, foreseen for 2014, it will perform a deep survey entire X-ray sky. soft band (0.5-2 keV), this be about 20 times more sensitive than ROSAT all sky survey, while in hard (2-10 keV) provide ever true imaging at those energies. Such all-sky revolutionize our view high-energy sky, and calls major efforts synergic, multi-wavelength wide area surveys order to fully exploit...
We describe the design of a new polarization sensitive receiver, spt-3g, for 10-meter South Pole Telescope (spt). The spt-3g receiver will deliver factor ~20 improvement in mapping speed over current spt-pol. sensitivity enable advance from statistical detection B-mode anisotropy power to high signal-to-noise measurements individual modes, i.e., maps. This lead precise (~0.06 eV) constraints on sum neutrino masses with potential directly address mass hierarchy. It allow separation lensing...
(Abridged) This is the first of a series papers in which we derive simultaneous constraints on cosmological parameters and X-ray scaling relations using observations growth massive, flux-selected galaxy clusters. Our data set consists 238 clusters drawn from ROSAT All-Sky Survey, incorporates extensive follow-up Chandra Observatory. Here describe implement new statistical framework required to self-consistently produce cosmology such data, present results models dark energy. In spatially...
(Abridged) This is the second in a series of papers which we derive simultaneous constraints on cosmology and X-ray scaling relations using observations massive, flux-selected galaxy clusters. The data set consists 238 clusters drawn from ROSAT All-Sky Survey with 0.1-2.4 keV luminosities >2.5e44 erg/second, incorporates extensive follow-up Chandra Observatory. Our analysis accounts self-consistently for all selection effects, covariances systematic uncertainties. Here describe reduction...
We employ robust weak gravitational lensing measurements to improve cosmological constraints from of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in ROSAT All-Sky Survey. Our analysis constrains absolute scale such at 8 per cent level, including both statistical systematic uncertainties. Combining it with survey data follow-up observations, we find a tight constraint on combination mean matter density late-time normalization power spectrum,...
The Suzaku satellite provides a census of the gas, metals, and dark matter out to outskirts Perseus Cluster.
We report weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known. This cluster sample, introduced earlier in this series papers, spans redshifts 0.15 < z_cl 0.7, and is well suited to calibrate mass proxies current cosmology experiments. Cluster are measured with a standard `color-cut' lensing method from three-filter photometry each field. Additionally, 27 fields at least five-filter photometry, we measure high-accuracy using new that exploits all information available...
This is the first in a series of papers which we measure accurate weak-lensing masses for 51 most X-ray luminous galaxy clusters known at redshifts 0.15<z<0.7, order to calibrate and other mass proxies cosmological cluster experiments. The primary aim improve absolute calibration observables, currently dominant systematic uncertainty count Key elements this work are rigorous quantification uncertainties, high-quality data reduction photometric calibration, "blind" nature analysis avoid...
(abridged) We present cosmological constraints obtained from galaxy clusters identified by their Sunyaev-Zel'dovich effect signature in the 2500 square degree South Pole Telescope Sunyaev Zel'dovich survey. consider 377 cluster candidates at z>0.25 with a detection significance greater than five, corresponding to 95% purity threshold for compute on models using measured abundance as function of mass and redshift. include additional multi-wavelength observations, including Chandra X-ray data...
This is the second in a series of papers studying astrophysics and cosmology massive, dynamically relaxed galaxy clusters. The data set employed here consists Chandra observations 40 such clusters, identified comprehensive search archive for hot (kT ≳ 5舁keV), morphologically systems, as well high-quality weak gravitational lensing subset these Here we present cosmological constraints from measurements gas mass fraction,舁 fgas, this cluster sample. By incorporating robust calibration X-ray...